#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <string.h>

int main()
{
	char arr1[] = "abcdefabcdef";
	char arr2[] = "def";
	 char* ret = strstr(arr1, arr2);
	ret[1] = '2';
	printf("%s\n", ret);
	return 0;
}
